![]() Our first goal of this work is to gain a fundamental understanding of the ground state geometric structures in medium-sized silicon clusters. In order to systematically study the structural evolution and electronic properties of silicon clusters, we here present extensive structure searches to explore the global minimum geometric structures of medium-sized neutral and charged silicon clusters in the size range of 20 ≤ n ≤ 30, by combining our developed CALYPSO method with the density functional theory. Moreover, the determination of the true global minimum structure is also a challenging problem, because of the much increased complexity of the potential surface as well as the exponential increase of the lowest-energy structure with the number of atoms in the cluster 21. (ii) The predicted global minima are subtle sensitivity for the selected density functional theory, or the molecular-orbital level in the ab initio calculations. The main reasons may be as follows: (i) The procedure used in the case of small clusters is not practical for larger clusters. Despite the enormous progress that has been made, the true lowest-energy structures for the silicon clusters in the size range of 20 ≤ n ≤ 30 are still debatable. A lot of works have been carried out with results not always in agreement between authors 14, 15, 16, 17, 18, 19, 20. Up to now, most of spherical and compact clusters have been considered as theoretical models attempting to support this measurement. However, the transition from prolate to more spherical-like geometries for cationic silicon clusters was observed in between 24 < n < 30 11, 12, 13, 14. have determined that anionic silicon clusters are prolate shape for n < 27 and become more spherical-like geometry for larger clusters 11. Ion mobility measurements have revealed much of what is known about the growth behaviors of medium-sized silicon clusters 14. Several high-resolution photoelectron, Raman and infrared spectra experiments have been carried out to understand the atomic structure of small silicon clusters and showed that both Si 6 and Si 10 have exceptional stability 11. Much attention has been focused on understanding the structural and growth behavior of small or medium-sized silicon clusters 4, 10, 11, 12, 13, 14. During the past two decades, a large number of experimental and theoretical studies have been carried out in this direction 4, 6, 7, 8, 9, 10. The study of the structures and properties of silicon clusters has been an extremely active area of current research. ![]() In this size regime, the structures and properties of materials often differ dramatically from those of the bulk. If current miniaturization trends continue, minimum device features will soon approach the size of atomic clusters. Silicon is the most widely used material in the microelectronic industry. The study of small clusters can help us to design better nanosystems with specific physical and chemical properties. The experimental and theoretical studies of the atomic and molecular clusters are interesting topics since they constitute intermediate phases between individual atoms and bulk solids, which can be used to understand how the fundamental properties of materials evolve from isolated atoms or small molecules to a bulk phase 1, 2, 3, 4, 5, 6, 7, 8. The HOMO-LUMO gaps and vertical ionization potential patterns indicate that Si 22 is the most chemical stable cluster, and its dynamical stability is deeply discussed by the vibrational spectra calculations. In addition, no significant structural differences are observed between the neutral and cation charged silicon clusters with n = 20–24, both of them favor prolate structures. These results are in good agreement with the available experimental and theoretical predicted findings. The growth behaviors clearly indicate that a structural transition from the prolate to spherical-like geometries occurs at n = 26 for neutral silicon clusters, n = 27 for anions and n = 25 for cations. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. A large number of low-lying isomers are optimized at the B3PW91/6-311 + G* level of theory. The structural and electronic properties for the global minimum structures of medium-sized neutral, anionic and cationic Si n μ ( n = 20–30, μ = 0, −1 and +1) clusters have been studied using an unbiased CALYPSO structure searching method in conjunction with first-principles calculations.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |